BI-Fuel/Alternative Fuels

Schematic:

CIRCUIT DESCRIPTION
The Oxygen Sensor (O2S) is used in order to determine the oxygen content of the engine's exhaust. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the engine is operating lean the exhaust will have more oxygen content. Once at operating temperature, the O2S will produce a voltage in relation to the oxygen content of the exhaust. The O2S requires an operating temperature of 360°C (600°F) to produce voltage. The O2S will produce more voltage when the exhaust is rich and less voltage when the exhaust is lean. The O2S operating voltage range is around 0.10 volts (100 mV) to 1 volt (1000 mV).

The gasoline control module (VCM / PCM or ECM) supplies a bias (or reference) voltage to the HO2S. This bias voltage is around 450 millivolts.

This DTC is used to indicate an O2S signal voltage that is above the normal operating range of the sensor.

CONDITIONS FOR RUNNING THE DTC
^ The engine is operating on alternative fuel.
^ Engine speed is greater than 500 RPM.
^ Engine coolant temperature is above 70°C (160°F).
^ The AF ECU determines the O2S has been at operating temperature for at least 2 minutes. The engine coolant temperature must be greater than 40°C (104°F) AND the calculated mass air flow must be above 6 grams per second for 2 minutes in order for the AF ECU to determine the O2S is at operating temperature.
^ The AF ECU is operating in Closed Loop fuel control.

CONDITIONS FOR SETTING THE DTC
The AF ECU monitors an O2S signal voltage of greater than 1 volt (1000 mV) for 3 seconds continuously.

ACTION TAKEN WHEN THE DTC SETS
The AF ECU will operate in Open Loop fuel control.
^ A first failure of this DTC will NOT illuminate the MIL and will store as Last Test Failed but not as History.
^ The AF ECU will illuminate the MIL and store the DTC as History after TWO consecutive drive trips that the diagnostic runs and fails.
^ The AF ECU will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The Last Test Failed status will clear when the DTC runs and passes.
^ The AF ECU will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes.
^ The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC.
^ All DTC Information can be cleared using a scan tool.
^ Interruption of Control Module (AF ECU / VCM / PCM or ECM) power or ground MAY clear DTC Information. Clearing DTC Information with this method is inconsistent and should not be performed.

DIAGNOSTIC AIDS
Fault Not Present
Fault Not Present indicates the condition that caused the DTC to set is intermittent and not currently present. Refer to Intermittent Conditions diagnostic information located in Symptoms-Computers and Control Systems. If any additional DTCs were stored, proceed to the applicable DTC table in the order stated in the Diagnostic System Check Alternative Fuels (Computers and Control Systems). Intermittent Conditions

TEST DESCRIPTION

Steps 1-5:

Steps 6-13:

Steps 14-15:

The numbers below refer to the step numbers on the diagnostic table.
3. An O2S contaminated by silicon will have a white, powdery deposit on the portion of the O2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of un-approved silicon RTV engine gasket material or the use of silicon based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement O2S will also get contaminated.
8. An O2S contaminated by silicon will have a white, powdery deposit on the portion of the O2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of un-approved silicon RTV engine gasket material or the use of silicon based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement O2S will also get contaminated.